1. Field of the Invention
The present invention relates to a voltage regulator configured to output voltage independent of ambient temperature.
2. Description of the Related Art
FIG. 4 is an illustration of a related-art reference voltage circuit configured to output voltage with a small change due to temperature. A related-art reference voltage circuit 10 is configured to average, with an averaging circuit 13, an output voltage Vref1 of a first reference voltage circuit 11 having a positive temperature coefficient, and an output voltage Vref2 of a second reference voltage circuit 12 having a negative temperature coefficient, and to adjust the averaged voltage to a predetermined voltage with a non-inverting amplifier circuit 14, thereby generating a reference voltage Vref with a small change due to temperature (for example, see Japanese Patent Application Laid-open No. 2004-30064).
A voltage VA of an output terminal (node A) of the averaging circuit 13 of the reference voltage circuit 10 is expressed by the following expression when a resistance value of each resistor of the averaging circuit 13 is represented by R, an output impedance of the first reference voltage circuit 11 is represented by Ro1, and an output impedance of the second reference voltage circuit 12 is represented by Ro2.VA={Vref1(R+Ro2)+Vref2(R+Ro1)}/(2R+Ro1+Ro2)
Here, the output voltage VA of the averaging circuit 13 has an error when the resistance value R is not such a large value that allows the output impedances Ro1 and Ro2 to be ignored, and when the output impedance Ro1 and the output impedance Ro2 differ from each other.
Further, the area occupied by the averaging circuit 13 is increased when the resistance value R is set to a large value.